Hydraulic fluids



Patented Dec. 21, 1937 UNITED STATES PATENT OFFICE HYDRAULIC FLUIDS No Drawing.

Application March 6, 1935,

Serial N0. 9,590

Claims. (Cl. 252 -5) This invention relates to compositions of matter and more particularly to fluids desirable for use in hydraulically operated apparatus such, for example, as hydraulic brakes and the like.

Various proposals @have been made to use mixtures of alcohol and castor oil, glycerine, and the like for the hydraulic transmission of power such as for actuating the pressure-operated elements of hydraulic brake systems and similarly operated m apparatus. Numerous disadvantages have, however, characterized these mixtures and solutions such as to give rise to dangerous possibilities in connection with brake systems. Wide change of viscosity, corrosive or decomposing effect upon parts of hydraulic apparatus, tendencies to gaslfication and/or solidification under higher and lower temperature conditions respectively, all of these and similar disadvantages have been draw backs to commercial utilization of previously proposed fluids.

It is an object of the present invention to overcome these and other undesirable characteristics and particularly to produce a hydraulic fluid which is characterized by a wide range of usefulness under most variable operating conditions.

Other objects and advantages of this invention will be apparent by reference to the following specification in which its preferred details and embodiments are described.

We have discovered that organic acids or organic acid alcohols containing in the molecule at least six carbon atoms, as well as unsaturated and/or hydroxyl groups, or derivatives of said acids or alcohols, exclusive of the glycerides, are particularly suitable for use as, or suitable as raw material for making, hydraulic fluid.

Thus, we may start with glyceryl trioleostearate (China wood oil), glyceryl trioleate (cottonseed oil), or the like, and may introduce one or more 4 hydroxy groups by any well known hydroxylation method and then proceed for the production of derivatives such as hereinafter described in connection with glyceryl triricinoleate.

While we may synthesize compounds containing 45 the necessary hydroxyl and unsaturated linkages in various ways, we prefer to start with a cheap,

natural, raw material such as glyceryl triricinoleate from which we obtain various alkyl or aryl ricinoleates by any well known process of radical interchange. Thus, we may obtain methyl, ethyl,

glycol, glyceryl, phenyl, cyclohexyl or like radicalcontaining ricinoleic esters.

We may also hydrogenate ricinoleic acid, glyceryl triricinoleate, or other ricinoleates, and pro- 55 duce ricinoleyl alcohol. .From this product we .case of the ricinoleates by radical interchange l5 and hydroxylation of the glyceride ester to alcohol and the like.

0f the broad class of compounds previously referred to, those that have been found especially useful in compositions for use in hydraulically operated systems are such as are hereinafter referred to as ricinol compounds. This term is used herein to designate generically ricinoleic acid and ricinoleyl alcohol or derivatives thereof containing the ricinoleyl radical. Ricinoleates that may 5 be employed include, for example, saturated monohydric aliphatic alcohol esters, such as the methyl, ethyl, propyls, butyls, etc. esters; saturated polyhydric aliphatic alcohol esters, such as monoor diethylene glycol, monoor dipropylene glycol, etc. esters; esters of aryl or aralkyl alcohol esters, such as the phenyl and benzyl esters; salts, such as the copper, lead, zinc, manganese, barium, ammonium, etc. ricinoleates. Ricinoleyl derivatives that may be used include, for example, ricinoleyl esters, of saturated aliphatic carboxylic acids, such as the formate, acetate, propionate, butyrates, glycollate, citrate, lactate, tartrate; of unsaturated aliphatic carboxylic acids, such as the oleate, linoleate, ricinoleate, etc.; ethers, such as the mixed ethers of ricinoleyl alcohol and methanol, ethanol, propanols, butanols, glycols, glycerol, etc.; inorganic esters, such as ricinoleyl phosphate, borate, nitrate, etc. Nitrogen-containing ricinol compounds can also be used, for example, ricinoleyl amines or ricinolamlde.

Although ricinol compounds per se are admirably fitted for hydraulic fluid purposes we have found that an improved fluid can also be obtained by utilizing such ricinol compounds in admixture or combination with one or more organic solvents or diluents. Among the organic materials suitable for admixture are: alcohols, such as the monoand polyhydric, aliphatic, alicyclic, aromatic and amino alcohols, such as methanol, propanol, isobutanol, octanol, diacetone alcohol, ethylene and propylene glycol, glycerol, sorbitol, cyclohexanol, phenol, benzyl alcohol, triethanolamine and ethoxyaminobutanol; organic esters such as ethyl and butyl acetate; ethers such as diisobutyl, ethyl tertiary butyl and methyl ricinoleyl ethers; aldehydes such as hept aldehyde and benzaldehyde; ketones such as diisopropyl ketone and cyclohexanone; nitrogencontaining compounds such as triethanolamine,

octyl amine, tetrahydrofurfuryl alcohol and fu-' rane compounds; hydrocarbons, such as isooctane, benzene, and cyclohexane.

A further advantage of the monoand polyhydric alcohol diluents resides in the fact that hydraulic fluid compositions which contain such alcohols have a much greater water tolerance than in the absence thereof.

Solvents or diluents as above illustrated may be used in ratiosto the ricinol compounds which vary over a wide range, although, generally speaking, we prefer to have at least about 10% ricinol compound present in our final composition.

As examples of representative hydraulic fluids of this invention, we have found that the following compositions have highly desirable characteristics:

' Per cent Isobutanol by volume 55 Glycerine do 13.5 Diethylene glycol 20.25 Methyl ricinoleate 10.

Per cent by volume Normal butanol 56.25 Glycerine 4.5 Propylene glycol 20.25 Ricinoleyl glycolate 10.00

Per cent by volume Isobutanol 50. Glycerine 13. Ethylene glycol 18.25 Octanol 2.00 Ricinoleyl tertiary butyl ether 16.25

Per cent by volume Ricinoleyl monoaminoacetate 15.00 Isobutylene glycol 32.00 Normal butanol 53.00

Per cent by volume Monoethylamine ester of ricinoleic acid v 20.3 Ethylene glycol 20.0 Propylene glycol 6.7 Isobutanol 50.0 Propanol 3.0

To 100 parts of this last composition is added 0.5 part of the suspension of graphite in water known under the trade marked name Aquadag, and 2 parts of potassium ricinoleate.

Hydraulic fluids are used under a wide range of climatic and artificial conditions involvinga considerable range of temperature, pressure, and the like. For example, such fluids when used in automotive mechanisms operate at temperatures that may vary from -50 F.. to above 150 F. This, in turn, requires fluidity at low temperatures and at the same time sufficient viscosity to permit operation at high temperatures.

Airplanes shock absorbers, artillery recoil mechanisms, hydraulic brakes, door checks, and the like also involve materials of construction such as aluminum, copper, bronze, steel and ferrous alloys as well as organic compounds such as rubber, synthetic resins and plastics. It is a requirement of high grade hydraulic fluids that none of these constructional materials be severally attacked or adversely affected.

The fluid must not freeze, boil or produce excessive vapor pressures or attack materials of construction to a considerable degree, and must possess satisfactory viscosities under all conditions. It must not have hygroscopicity which will interfere with normal operation of the apparatus. In contact with air or other gases it must not dissolve sufllcient quantities of air or other gases when brought in contact with them that under operating conditions suflicient gas should be released to cause vapor look.

In order to comply with all these requirements we have found that in the case of certain diluents it is preferable to add a solubilizing agent to the ricinol compound-diluent mixture, and in such cases we have found that various materials or combinations of materials are suitable. Thus. for example, in the case of mixtures of ricinol compounds and petroleum hydrocarbons we have found that, although not normally appreciably soluble in one another, the addition of alkyl ricinoleate, such as ricinoleyl hydroxy stearate, glycol stearate and octyl-2 methyl pentyl recinoleate, or the higher, branched chain alcohols obtainable by the catalytic hydrogenation of oxide of carbon, such as 2-5 dimethyl octanol-l 4-7 dimethyl pentanol-2, and the like, completely solubilizes the mixture and produces a highly desirable hydraulic fluid. Thus, we have found a composition of the following to COZIStitI itG a well solubilized, desirable hydraulic fluid:

1 Per cent Normal butanol 62.5 Propylene glycol 10 Light lubricating oil l5 Ethylene glycol monoricinoleate Fraction of branched chain higher alcohols obtainable by catalytic hydrogenation of oxide of carbon and boiling above 200 C 2.5

Another method of solubilization according to this invention is accomplished "by the use of emulsifying agents which produce permanent minutely divided two phase systems, e. g. by the use of cellulose ethers, methyl or ethyl cellulose,

glycol cellulose, polyalcohol derivatives, such as glycol stearate, alcoholic amines such as ethanol amines, and the like.

We have found that the lubricating qualities of the hydraulic fluids of this invention may be even further improved by the addition of assisting lubricants, such as deflocculated graphite, or extreme pressure lubricants, such as the phosphates and nitrates of the mixture of synthetic higher straight chain aliphatic alcohols produced by reduction of fatty acid glycerides, such as cocoanut oil, to acids, tricresyl phosphate, ricinoleyl phosphate, and the like; metal soaps such as potassium oleate, and the like.

. We have also found that these assisting lubricants have a particularly advantageous value in lowering the pour point at temperatures slightly above that at which the lubricant solidifies. Illustrative of this, and other features of this invention, is the following highly desirable fluid composition which we have prepared: by vol,- ume of the mixed monopropylene and mono isobutylene glycol ricinoleates, 32% of propylene glycol, 53% of normal butanol. To 100 parts of this mixture was added 0.5 part of the sus- 'admixed as follows: 70%

pension of graphite in castor 011 known under the trade marked name of "Castordag.

In like manner as the lubricating qualities oi the fluids of this invention may be improved, we have found that corrosion of the operating parts with which the fluids come in contact, if ordinarily occurring, may be overcome by use of corrosion inhibitors, without adversely affecting the advantageous characteristics of our fluid. Various materials may be utilized for inhibition of corrosion which, in some instances, also fill the role of assisting lubricants, such as above described, and/or other additional functions. Thus, for example, we may utilize alkali metal oleates, ricinoleates, abietates, arsenites, benzoates, phosphates, chromates, isopropyl sulfon ates, dichromates, nitrites, dior triethanol amines, glucamines, sulfurated castor oil, sulfonic acid salts of oleic acid, the sulfated products produced from synthetic aliphatic higher alcohols, such as lauryl alcohol, and the like as corrosion inhibitors.

The. proportion of corrosion inhibitor to the hydraulic fluid proper may be widely varied, particularly if it is also acting to fulfill other functions, such, for example, as those of an assisting lubricant. We prefer, however, to utilize the corrosion inhibitor in relatively small quantities such as not greatly exceeding, say 0.2-% of the total composition.

Illustrative of combined assisting lubricant, pour point depressant and corrosion inhibitor functions is the sodium oleate of the following fluid composition of this invention: 50% of isobutanol by volume, 18.75% diethylene glycol, 20.25% propylene glycol, ethylene glycol monoricinoleate; 2.4 parts by weight of sodium oleate is added to 100 parts by weight of this mixture.

Although we prefer to utilizea ricinol compound, as such or together with other added ingredients, in the absence of water, we have found that the usual disadvantageous effect of the, perhaps fortuitous, presence of water and consequent lack of surface wetting, may be over come, by the addition of relatively small quantities of a vegetable oil or other reagent which solubilizes the water in the fluid, such as Cellosolve, cocoanut oil, oleate esters, or the like.

In order to obtain a fluid, such as previously described, which possesses suflicient body at the extremes of temperature that may be encountered in automotive operation, we have found it sometimes desirable, in preparing our fluid. to add materials as bodying agents, such as metal stearates, particularly aluminum, calcium and magnesium stearates, cellulose compounds, such as masticated cellulose, glycol cellulose, and methyl cellulose, gum tragacanth, cyclohexanolamine stearate, alginic acid salts, and the like. A fluid composition of the present invention in which is incorporated a bodying agent may be monohydric alcohol consisting of 55 parts of butyl alcohol, 10 parts of mixed amyl alcohols and 5 parts of hexyl and heptyl alcohols, ethylene glycol monoricinoleate, 15% propylene glycol monoricinoleate. To 100 parts of this mixture was added 3 parts of low substituted methyl cellulose.

Similarly materials may be added, according to this invention, which depress the pour point of our fluid, such as octadecanediol ether, molasses, glucose, sorbitol, the suspensions of graphite in castor oil, known under the trade-marked name Casto'rdag, suspensions of graphite in water known under the trade-marked name of Aquadag", suspensions of graphite in glycerine known under the trade marked name of Glydag", and the like.

Although the hydraulic fluid of this invention has been described as desirable by itself for use in hydraulically operated systems, it willbe understood that it may likewise be incorporated as a desirable addition to, or a substitution for varying amounts of, the constituents of now known hydraulic fluids. Thus, for example, 50 parts ethyl alcohol is mixed with 50 parts ethylene glycol monoricinoleate; 50 parts of diacetone alcohol is mixed with 50 parts ethylene glycol monoricinoleate. To 100 parts of each of these mixtures may be added 2 parts of a metal salt, such as potassium oleate, to serve as a corrosion inhibitor.

Likewise to 65 parts of monoethyl ether of ethylene glycol may be added 35 parts of ethylene glycol monoricinoleate or other ricinol compound of this invention. We may also, as in other fluids, add to such" mixturesgvarying amounts of corrosion inhibitors, pour point depressants, assisting lubricants, and the like, such as previously described.

Although the fluids of this invention, containing as essential ingredients ricinol compounds, are not reactive toward oxidizing or gumming agents under normal conditions of use, nevertheless for extremely severe oxidizing conditions we have found that the addition of minute quantitles of anti-oxidants or phenolic bodies tend to inhibit even incipient oxidation and gumming. Such bodies are illustrated by phenols, such as 3, 4, S-triaminophenol, paraaminophenol, pyrogallol and amines such as 2,4-diamino-4, hydroxy diphenylamine, paraaminodiphenyl amine, phen- 1ifiialphanaphthylamine, diphenylamine, and the Various changes may be made in the present invention without departing therefrom or sacrificing any of the advantages thereof.

We claim:

1. A substantially non-aqueous fluid for use in fluid pressure apparatus comprising an organic solvent diluent and a compound containing the ricinoleyl radical.

2. A substantially non-aqueous fluid for use in fluid pressure apparatus comprising an organic solvent diluent and ricinoleyl alcohol.

3. A substantially non-aqueous fluid for use in fluid pressure apparatus comprising an organic.

solvent diluent and a ricinoleyl ester.

4. A substantially non-aqueous fluid for use in fluid pressure apparatus comprising an organic solvent diluent and a ricinoleyl amine.

5. A substantially non-aqueous fluid for use in fluid pressure apparatus comprising an organic sovent diluent and a compound containing the ricinoleyl radical, the organic solvent diluent being present in the larger proportion.

6. A substantially non-aqueous fluid for use in fluid pressure apparatus comprising an organic solvent diluent and ricinoleyl alcohol, the or ganic solvent diluent being present in the major proportion.

7. A substantially non-aqueous fluid for use in fluid pressure apparatus comprising an organic solvent diluent and a ricinoleyl ester, the organic solvent diluent being present in the major proportion.

8. A substantially non-aqueous fluid for use in fluid pressure apparatus comprising an organic solvent diluent and a ricinoleyl amine, the orsonic solvent diluent being present in the major 10. A substsntiniiy non-aqueous fluid for use in proportion. v fluid pressure apparatus comprising isobutnnol 0. A substantially non-aqueous fluid for use in and ricinoieyi alcohol, the isobutenoi being presi'iuid pressure apparatus comprising an organic ent inthe major proportion. solvent diluent and n compoimd contaiinina the ricinoleyl radical, the compound containing the 1 JOHN C. WOODHOUSI. ricinoleyl radical being present to the extent of ARTHUR G. etieestabout 10% ottheiinalcomposition. 

